B
We have a machine that has initiated movement inexplicably, without operator input. The only way in the PLC program for that to happen is if the PLC is seeing two pushbutton inputs, and a prox input. The process that's initiates will latch on until it's complete, so it's possible that a momentary flicker on these inputs would initiate the machine.
How likely is it for the PLC to see a false positive on the inputs? I can think of a few possibilities, but maybe some of you with more experience than myself could give me an idea how plausible? Or other possible causes?
- Noise on the input wires, possibly the wire itself (1-10 feet stranded) acting as an antenna
- Ground fault, possibly the potential of the PLC and all inputs could go low enough to cause a false positive on all inputs simultaneously, just a brief flicker of ~1ms
- Glitch in the PLC firmware? Our logic is robust, but the process does latch on with the presence of 3 inputs until the process completes. Is it possible that a glitch in the PLC firmware could cause a 1-cycle glitch on an input or a bit somewhere in memory?
The PLC is a GE VersaMax Micro
How likely is it for the PLC to see a false positive on the inputs? I can think of a few possibilities, but maybe some of you with more experience than myself could give me an idea how plausible? Or other possible causes?
- Noise on the input wires, possibly the wire itself (1-10 feet stranded) acting as an antenna
- Ground fault, possibly the potential of the PLC and all inputs could go low enough to cause a false positive on all inputs simultaneously, just a brief flicker of ~1ms
- Glitch in the PLC firmware? Our logic is robust, but the process does latch on with the presence of 3 inputs until the process completes. Is it possible that a glitch in the PLC firmware could cause a 1-cycle glitch on an input or a bit somewhere in memory?
The PLC is a GE VersaMax Micro